Effect of annealing temperature on structural, electrical, and UV sensing characteristics of n-ZnO/p-Si heterojunction photodiodes

Abstract

The aim of this study is to investigate the influences of annealing temperature on initial device characteristicsand their correlations with ultraviolet (UV) radiation sensitivity of n-type zinc oxide/p-silicon (n-ZnO/p-Si) heterojunctionphotodiodes. Evolutions on the crystalline structure, surface morphology, ideality factor, barrier potential, interfacestate density, and donor concentration were systematically analyzed during the initial device characterizations beforetesting the UV sensitivities of the photonic devices. The results demonstrate that the sensitivity of each n-ZnO/p-Siphotodiode annealed at various temperatures was linearly correlated with different UV illumination intensities. Thedevices annealed at 750 ◦ C and 550 ◦ C exhibit more sensitive performance than devices annealed at 150 ◦ C and 350◦ C owing to lower dark currents and good oxide quality. However, the presence of an interfacial suboxide or silicateoxide layer significantly decreased the responsivity of the photodiodes annealed at 750 ◦ C. The maximum responsivityvalue was 126 mA/W for the photodiode annealed at 550 ◦ C. It can be concluded that the photodiode annealed at550 ◦ C exhibits promising performance for UV sensing applications.